Electric switch



Dec. 27, 1938. A. CIANCHI 2,142,046

ELECTRIC SWITCH Filed Aug. 26, 1957 Fig.1. L 5 Fig.2

I 1 UT 1/ 1 Fig.3. /2

Patented Dec. 27, 1938 UNITED STATES PATENT OFFICE Application August 26, 1937, Serial No. 161,141 In Great Britain August 31, 1936 1 Claim.

This invention relates to electric switches of the kind in which a vessel encloses a quantity of mercury or other conducting liquid and a plunger made of or having a part made of mag- 5 netic material, and forming an armature which is acted upon by magnetic means to cause it to move and move the liquid or some of the liquid and thus to establish or disestablish electrical connection between the contacts. Thus, the arma- 10 ture may constitute or form part of a plunger which merely changes the level of a body of mercury to cause it to make or break electrical connection between the contacts, or the plunger may be provided with a cup containing conducting liq- 15 uid which when the plunger is lowered comes into communication with another body of conducting liquid to establish connection and which when the plunger is raised is separated from the other body of liquid to disestablish it.

20 According to the invention such a switch is provided with means for arresting the armature and with means for releasing it. Thus the armature may be arrested in the position into which it is moved magnetically. The arresting means 25 is arranged to spring or snap into place to arrest the armature so that it is retained in that position when the magnetic means ceases to act on the armature and it is withdrawn magnetically; the releasing means when operated then enables 30 it to return automatically to its initial position.

The invention will now be described with reference to the accompanying drawing, the figures of which illustrate three examples of switches made in accordance with it. Each of the figures 35 is a vertical longitudinal section.

Referring first to Figure 1, l is the switch vessel enclosing the inner ends of two contacts 2 and 3 which pass through the wall of the switch vessel l at the upper and lower ends and in which L they are fused. 4 is a plunger in the form of a tubular glass vessel which floats in a quantity of mercury 5 contained in the vessel l. The lower part of the plunger 4 forms a cup containing a quantity of mercury 6 into which dips the .5 lower end of the upper contact 2. The lower contact 3 is permanently immersed in the mercury 5. The plunger 4 has an opening 1 spaced from its lower end. At its'upper end it carries a tubular armature 8 of iron which fits over it.

0 A solenoid 9 surrounds the vessel l at a point below that occupied when the plunger 4 occupies the normal position shown. When the solenoid 9 is energized it pulls the plunger 4 down in the vessel l until eventually mercury 5 flows 5 through the opening 1 and communicates with the mercury 6 in the plunger 4 so as to establish electrical connection between the contacts 2 and 3. When the solenoid is de-energized the plunger 4 rises due to its buoyancy, any excess mercury in the plunger 4 flowing out of the opening 5 5 back into the main body 5 so as to re-establish the conditions shown.

The vessel I is provided with a laterally-extending side limb l0 in which there slides a mem ber ll provided with an outer sleeve I2 of mag-- 10 netic material. The member H is urged by a spring I3 into contact with the outer surface of the armature 8 which is curved in the longitudinal direction as shown. The limb I0 is surrounded by a solenoid l4. The arrangement is such that when the solenoid 9 draws the plunger 4 down the member I l snaps over the top edge of the armature 8 so that it arrests the plunger 4 in the down position if the solenoid 9 is now de-energized. The parts are retained in this position to maintain contact between contacts 2 and 3 until the member H is withdrawn to release the plunger. This is done by energizing the solenoid l4, whereupon the plunger 4 rises due to its buoyancy, and re-establishes the original condition. The two solenoids are conveniently connected to a source of current !5 by way of push-button switches I 6 and I! as indi cated. Pressure on button It causes solenoid 9 to be energized to establish contact through the switch I while pressure on button l1 energizes solenoid l4 to release the plunger 4 and allow it to rise to disestablish electrical connection.

Fig. 2 illustrates a mercury switch in which contact is made or broken merely as a result of raising or lowering the surface of a quantity of mercury 5 as a result of varying the extent of immersion in it of a plunger 4. The plunger 4 is provided with a separate armature 8 in the example illustrated, although the plunger 4 itself could constitute the armature. The plunger 4 is drawn down by the solenoid 9 to raise the level of mercury 5 and cause it to bridge the contacts 2 and 3. Fig. 3 shows the same switch in which 5 the solenoid 9 is de-energized and the plunger 4 is floating in the mercury 5, the level of which has fallen to dis-establish connection between 2 and 3. The plunger 4 of the switch of Figs, 2 and 3 is held down by spring catches I0 which are arranged on the interior of a tube and are repelled from the tube when the solenoid I 4 is energized to cause their lower ends to disengage from the top of the plunger 4 and allow it to rise.

I claim:-

An electric switch comprising a vessel, contacts therein, a conducting liquid within said vessel, a freely movable plunger floating in said liquid, an armature of magnetic material associated with the plunger, means adapted to act upon said armature magnetically to vary the extent of immersion of said plunger in said liquid thereby to open or close the circuit through said contacts, and a spring catch comprising a magnetic armature mounted in and on said vessel adapted 

